It is generally your responsibility to arrange any visa's applicable to a destination you are hoping to / booked to travel to , Love holidays are an OTA , and it is probably will say exactly that in the general terms and conditions .
I am a travel agent working from home , and would always tell my customers if a visa is needed as part of the service , and any good TA would have told you also , one of the pitfalls of booking online unfortunately it bypasses the personal service knowledge and experience of a good travel agent .

I agree with kerry25. If you are going outside Europe, the chances are you'll probably need a visa of some sorts, and It's up to you to either ask the question, or find out on forums like this before you travel.
As I've just said on another thread.

Research, research, research. More so if going medium to long haul.

The info about needing a visa is quite clear on the tour operators websites if you book direct, so the information would have been in the confirmation etc you got from the tour operator. It is always the passengers responsibility to check they have the correct entry documentation, whether that's a visa or just long enough validity on their passport. Take responsibility for yourself, and never rely on someone else to do your research for you.